International Association for Cryptologic Research

International Association
for Cryptologic Research


The supersingular Endomorphism Ring and One Endomorphism problems are equivalent

Aurel Page , Univ. Bordeaux, CNRS, INRIA, Bordeaux INP, IMB, UMR 5251, F-33400 Talence, France
Benjamin Wesolowski , ENS de Lyon, CNRS, UMPA, UMR 5669, Lyon, France
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Presentation: Slides
Conference: EUROCRYPT 2024
Abstract: The supersingular Endomorphism Ring problem is the following: given a supersingular elliptic curve, compute all of its endomorphisms. The presumed hardness of this problem is foundational for isogeny-based cryptography. The One Endomorphism problem only asks to find a single non-scalar endomorphism. We prove that these two problems are equivalent, under probabilistic polynomial time reductions. We prove a number of consequences. First, assuming the hardness of the endomorphism ring problem, the Charles--Goren--Lauter hash function is collision resistant, and the SQIsign identification protocol is sound for uniformly random keys. Second, the endomorphism ring problem is equivalent to the problem of computing arbitrary isogenies between supersingular elliptic curves, a result previously known only for isogenies of smooth degree. Third, there exists an unconditional probabilistic algorithm to solve the endomorphism ring problem in time $\tilde O(p^{1/2})$, a result that previously required to assume the generalized Riemann hypothesis. To prove our main result, we introduce a flexible framework for the study of isogeny graphs with additional information. We prove a general and easy-to-use rapid mixing theorem.
  title={The supersingular Endomorphism Ring and One Endomorphism problems are equivalent},
  author={Aurel Page and Benjamin Wesolowski},